In recent years, there have been advances in provision of laws relating to resource measures such as the approval of the Law for the Promotion of Effective Utilization of Resources, and there is now active endeavor to grapple with recycling products back into resources, reusing resources and reducing waste. In particular, for household electrical appliance and electronic equipment manufacturers, recovery and recycling of sold products has become an important issue.
For example, with various personal computers, printers, mobile phones and so on, a resin material is often used as a material constituting the casing from the viewpoint of moldability, light weight and so on. In such fields, establishment of recycling technology for resin casings is thus strongly called for.
Examples of recycling technology for resin casings are thermal recycling technology in which resin casings are used as a heat source, and recycling technology for cascade use in which it is possible to not consider the deterioration in material properties of the recycled resin obtained through recycling the resin casings that much. Following is a concrete description of one example of a method for producing recycled resin in recycling technology for cascade use with reference to FIG. 6. First, various recovered personal computers, printers, mobile phones and so on are dismantled, and the resin casings contained therein are sorted and recovered (dismantling/recovery step S1′). Next, unwanted matter, i.e. attachments such as labels and rubber feet, metal components such as screws and springs, and soiling such as dust is removed from the sorted and recovered resin casings (removal step S2′). Next, sorting is carried out (sorting step S3′) by discriminating the materials of the resin casings from which the unwanted matter has been removed using material indications displayed on the resin casings (material discrimination step S31′), carrying out discrimination as to whether or not a fire retardant has been added using a fire resistance test (e.g. UL94 combustion test method) (fire resistance testing step S32′), and carrying out discrimination of color differences using the naked eye (color difference discrimination step S33′). Next, the sorted resin casings are crushed using a crusher (crushing step S5′). Through passing through such steps, recycled resin can be obtained from the recovered products (various personal computers etc.).
However, the extent of deterioration of a resin contained in a resin casing varies greatly according to the state of use of the recovered product, and hence with a resin material containing recycled resin obtained using recycling technology as shown in FIG. 6, it has been difficult to stably obtain material properties, attractive appearance and so on to the same level as with a virgin resin material. It has thus been difficult to use a resin material containing recycled resin as a molding material for resin casings (e.g. resin casings that constituted recovered products) required to have high fluidity and high strength.
Art that enables material properties of a resin material containing recycled resin obtained using recycling technology to be obtained to the same level as with a virgin resin material has thus become publicly known as disclosed in Japanese Patent Application Laid-open No. 2000-198116 and Japanese Patent Application Laid-open No. 2001-30248.
However, with the art disclosed in Japanese Patent Application Laid-open No. 2000-198116 and Japanese Patent Application Laid-open No. 2001-30248, sorting of the materials of the resin casings of recovered products is not carried out, and hence in the case that various materials of resin casings of recovered products are present mixed together, it becomes difficult to maintain the material properties of a resin material containing recycled resin obtained using the recycling technology at the same level as with a virgin resin material. Moreover, a metal separation step such as a magnetic sorting step is carried out a plurality of times, but each of these steps is carried out after the crushing step. Consequently, in the crushing step of crushing the resin casings using a crusher, in the case that metal components or the like remain, these metal components will be crushed together with the resin casings, and hence damage to the crusher will be increased. In addition, the amount of metal to be removed after the crushing will be relatively high, and hence the amount of resin removed together with metal due to being attached to the metal may increase, and thus the resin recovery efficiency may drop.